Linkage isomerism occurs in coordination compounds where the ligand can coordinate through different atoms. One common example is the linkage isomerism in nitro and nitrito complexes.

Consider the complex [Co(NH₃)₅(NO₂)]²⁺. Here, the nitro ligand (NO₂) can bind to the central cobalt atom either through the nitrogen atom (forming a nitro ligand) or through one of the oxygen atoms (forming a nitrito ligand).

So, the two possible linkage isomers of this complex are:

1. [Co(NH₃)₅(NO₂)]²⁺ (Nitro linkage isomer)
2. [Co(NH₃)₅(ONO)]²⁺ (Nitrito linkage isomer)

In the nitro linkage isomer, the nitrogen atom of the NO₂ ligand is coordinated to the cobalt atom, while in the nitrito linkage isomer, one of the oxygen atoms of the NO₂ ligand is coordinated to the cobalt atom.

Coordination isomerism occurs when both cation and anion in a complex ion are exchanged with each other. Here's an example:

Consider the coordination compounds [Co(NH₃)₅Cl]Cl₂ and [CoCl₅(NH₃)]²⁻.

In the first compound, [Co(NH₃)₅Cl]Cl₂, the cobalt ion is surrounded by five ammonia ligands and one chloride ion. The counter ion is another chloride ion.

In the second compound, [CoCl₅(NH₃)]²⁻, the cobalt ion is surrounded by five chloride ions and one ammonia ligand. The counter ion is a neutral ammonia molecule.

In both cases, the coordination sphere of cobalt is different, but the overall formula of the compounds remains the same. This is an example of coordination isomerism.

Sure, here are two examples of ligands commonly used in coordination compounds for analytical chemistry:

1. Ethylenediamine (en): Ethylenediamine is a bidentate ligand, meaning it can coordinate to a central metal ion through two of its nitrogen atoms. This ligand forms stable complexes with many metal ions, such as copper, cobalt, and nickel. In analytical chemistry, ethylenediamine complexes are often used in qualitative and quantitative analysis of metal ions in solution, including complexometric titrations.

2. 1,10-Phenanthroline: 1,10-Phenanthroline is a heterocyclic aromatic compound that acts as a chelating ligand. It forms stable complexes with various metal ions, including iron, copper, and zinc. These complexes are often intensely colored, making them useful for colorimetric determination of metal ions in solution. 1,10-Phenanthroline complexes are widely used in analytical chemistry for applications such as spectrophotometric analysis and metal ion detection.